Net Loss per Share - Summary of Basic and Diluted Net Loss per Share Attributable to Common Stockholders (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Numerator:
Net loss	$ (24,986)	$ (17,717)	$ (13,150)	$ (5,072)	$ (10,599)	$ (10,463)	$ (9,956)	$ (10,644)	$ (60,925)	$ (41,662)
Denominator:
Weighted average common shares outstanding, basic and diluted	19,052,827	18,659,079	17,667,620	17,221,120	17,736,996	17,471,462	14,376,529	14,369,182	18,160,525	16,001,832
Net loss per share, basic and diluted	$ (1.31)	$ (0.95)	$ (0.74)	$ (0.29)	$ (0.60)	$ (0.60)	$ (0.69)	$ (0.74)	$ (3.35)	$ (2.60)